Merge pull request #24216 from dkurt:inter_lines_less_compute

Minor optimization of two lines intersection #24216

### Pull Request Readiness Checklist

Not significant, but we can reduce number of multiplications while compute two lines intersection. Both methods are used heavily in their modules.

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/objdetect/src/qrcode.cpp

@@ -68,19 +68,14 @@ static void updatePointsResult(OutputArray points_, const vector<Point2f>& point
 
 static Point2f intersectionLines(Point2f a1, Point2f a2, Point2f b1, Point2f b2)
 {
+    // Try to solve a two lines intersection (a1, a2) and (b1, b2) as a system of equations:
+    // a2 + u * (a1 - a2) = b2 + v * (b1 - b2)
     const float divisor = (a1.x - a2.x) * (b1.y - b2.y) - (a1.y - a2.y) * (b1.x - b2.x);
     const float eps = 0.001f;
     if (abs(divisor) < eps)
         return a2;
-    Point2f result_square_angle(
-                              ((a1.x * a2.y  -  a1.y * a2.x) * (b1.x - b2.x) -
-                               (b1.x * b2.y  -  b1.y * b2.x) * (a1.x - a2.x)) /
-                               divisor,
-                              ((a1.x * a2.y  -  a1.y * a2.x) * (b1.y - b2.y) -
-                               (b1.x * b2.y  -  b1.y * b2.x) * (a1.y - a2.y)) /
-                               divisor
-                              );
-    return result_square_angle;
+    const float u = ((b2.x - a2.x) * (b1.y - b2.y) + (b1.x - b2.x) * (a2.y - b2.y)) / divisor;
+    return a2 + u * (a1 - a2);
 }
 
 //      / | b